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<STRONG><U>II.3 Tailoring the Cables</U></STRONG>
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Application programs are uploaded to the target system over a serial
interface. The serial ports of the PC may have <NOBR>9-pin</NOBR> or
<NOBR>25-pin</NOBR> male <NOBR>D-Shell</NOBR> connectors. Suitable
<NOBR>RS-232</NOBR> cables for the <NOBR>MCS-51</NOBR> board can be
tailored as follows:
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<IMG SRC="cable25s.gif" ALT="RS-232 cable with 25-pin female D-Shell connector" WIDTH=460 HEIGHT=230>
<BR>RS-232 cable with 25-pin female D-Shell connector
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Shortening the modem control signals is absolutely required for batch
operation under <NOBR>MS-DOS</NOBR>! If the CTS-, DSR-, or DCD-input is not
set to logic low <NOBR>(+12V)</NOBR>, the PC will hang during character
output to the serial port.<BR>
For shell script operation under Linux, only the Tx-, Rx-, and ground
lines are required, and the handshake inputs may be left open.
The same is true for interactive operation with most terminal emulation
programs. (For further information refer to the documentation of your
terminal emulation program.)<BR>
If there is a spare <NOBR>RS-232</NOBR> line receiver on your
<NOBR>MCS-51</NOBR> board, it can be employed as a reset input! In this
case, the target system can be reset in batch (or script) files with the
<STRONG>reset</STRONG> program provided, and from terminal emulation programs
(by dropping the DTR output with the <NOBR>hang-up</NOBR> function).
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<IMG SRC="cable9s.gif" ALT="RS-232 cable with 9-pin female D-Shell connector" WIDTH=460 HEIGHT=230>
<BR>RS-232 cable with 9-pin female D-Shell connector
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If you own a <NOBR>9/25-pin</NOBR> mouse adaptor with all pins connected,
the <NOBR>9-pin</NOBR> version of the cable should be preferred!<BR>
If your <NOBR>MCS-51</NOBR> board has no spare <NOBR>RS-232</NOBR> line
receivers, but a TTL reset input (or you can establish one), the target
system can also be reset in batch (or script) files over a printer port of
the PC. For this, a suitable reset cable must be tailored as shown below:
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<IMG SRC="cable25p.gif" ALT="Reset cable with 25-pin male D-Shell connector" WIDTH=460 HEIGHT=120>
<BR>Reset cable with 25-pin male D-Shell connector
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In practice, only one of the two reset lines will be required.
When the <STRONG>reset</STRONG> program is invoked, a positive reset pulse appears
at D0 (8031, 8032), and a negative pulse at D1 (80C535, 80C537).
For detailed information on the <STRONG>reset</STRONG> program, refer to chapters
<NOBR><A HREF="bbatch.htm">III.2 Batch File Operation under MS-DOS</A></NOBR>, and
<NOBR><A HREF="bscript.htm">III.4 Shell Script Operation under Linux</A></NOBR>.
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